Optical lens and light emitting device using the same

ABSTRACT

A light emitting device includes a light-emitting semiconductor unit and an optical lens coupled to the light-emitting semiconductor unit. The optical lens includes a top surface, a base portion opposite to the top surface, and a peripheral side surface defining a first refractive portion. The top surface is generally funnel-shaped. The first refractive portion is corrugated with a plurality of protruding ridge structures, each including a refractive surface.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional application of U.S. patentapplication Ser. No. 11/697,304, filed on Apr. 6, 2007, which claimsforeign priority based on Chinese Patent Application No. 200610200892.2,filed in China on Sep. 22, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The disclosure generally relates to optical lenses for light emittingdevices and, particularly, to an optical lens typically used for a sideemitting light-emitting diode (LED).

2. Discussion of the Related Art

LEDs are widely applied in electronic display devices and illuminatingdevices, offering advantages of high illumination efficiency and a longlifetime. An LED generally includes a semiconductor chip emitting light.LEDs can be classified, according to the location of the semiconductorchip therein, as bottom emitting LEDs and side emitting LEDs.

Referring to FIG. 1, in a typical bottom emitting LED, a semiconductorchip 11 is disposed below a display screen 12. The semiconductor chip 11is configured for emitting multiple colors of light, such as red, green,and blue (RGB). A distance D1 between the semiconductor chip 11 and thedisplay screen 12 must be sufficient to provide a predeterminedthreshold angle from which the RGB light is emitted from thesemiconductor chip 11. The emitted RGB light can thus be adequatelymixed to yield white light illuminating the display screen 12. Thedistance D1, however, is apt to increase a thickness of the bottomemitting LED, thereby increasing the overall size of the device.

Referring to FIG. 2, in a typical side emitting LED, a display screen 22is stacked on a light guide plate 24, and a semiconductor chip 21 isdisposed on at one side of the combined display screen 22 and lightguide plate 24. Light emitted from the semiconductor chip 21 travelsalong light paths including light paths 23 (only one of many is shown).The light paths 23 are located within the light guide plate 24, so thatthe light can be reflected continuously until exiting a top of the lightguide plate 24 and illuminating the display screen 22. The side emittingLED provides improved uniformity of light illuminating the displayscreen 22. However, light energy can be lost with each reflection, thusthe side emitting LED is limited in light utilization efficiency. Inaddition, in the case of a large display screen 22, some areas of thedisplay screen 22 may not be sufficiently illuminated.

FIG. 3 shows an optical lens 31 in another bottom emitting LED. Theoptical lens 31 is configured to improve the efficiency of lightutilization. The optical lens 31 includes a base portion 32, a topreflecting surface 34, a peripheral first refracting surface 36obliquely angled with respect to a central axis 35 of the optical lens31, and a peripheral, curved second refracting surface 38 extending froma bottom of the base portion 32 to the first refracting surface 36. Thebase portion 32 defines a bottom cavity (not labeled) therein. A bottomsurface of the base portion 32 is shaped like a flat-topped dome. Asemiconductor chip (not shown) can be disposed in or below the bottomcavity. Typically, the semiconductor chip emits light from a point “F”as shown. Light entering the optical lens 31 through a central flatportion of the bottom surface of the base portion 32 in the cavitypropagates to the reflecting surface 34. The light is reflected by thereflecting surface 34 to the first refracting surface 36. The light isrefracted by the first refracting surface 36, and exits the optical lens31 in a direction substantially perpendicular to the central axis 35.Light entering the optical lens 31 through a peripheral curved portionof the bottom surface of the base portion 32 in the cavity propagates tothe second refracting surface 38. The light is refracted by the secondrefracting surface 38, and exits the optical lens 31 in a directionsubstantially perpendicular to the central axis 35.

The optical lens 31 may be employed in side light-emitting devices, sothat the side light-emitting devices may be advantageously used withlight guides and reflectors that have very thin profiles and/or largeilluminated areas. However, each of the first refracting surface 36 andthe second refracting surface 38 is a single smooth peripheral surface.Thus it is difficult to manufacture the optical lens 31 to achievedesired light distribution characteristics and optimum light emittingangles. In addition, if the light incidence angle at the central flatportion of the bottom surface of the base portion 32 is not within apredetermined range, the light may escape from the optical lens 31through the reflecting surface 34 rather than reflecting to the firstrefracting surface 36. When this happens, the efficiency of lightutilization is reduced.

Therefore an optical lens which can overcome the above-describedshortcomings is desired, as is a light emitting device employing theoptical lens.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the drawings are not necessarily drawn to scale, theemphasis instead being placed upon clearly illustrating the principlesof the present optical lens and light emitting device. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views, and all the views are schematic.

FIG. 1 is an isometric view of parts of a frequently used bottomemitting LED.

FIG. 2 is a side view of the LED of FIG. 1, showing an essential opticalpath thereof.

FIG. 3 is a cross-section of an optical lens in another kind offrequently used bottom emitting LED.

FIG. 4 is a plan view of a light emitting device in accordance with afirst embodiment of the disclosure.

FIG. 5 is a cross-section of the light emitting device shown in FIG. 4.

FIG. 6 is similar to FIG. 5, but shows essential optical paths of thelight emitting device.

FIG. 7 is a cross-section of an optical lens in accordance with a secondembodiment of the disclosure.

FIG. 8 is a cross-section of an optical lens in accordance with a thirdembodiment of the disclosure.

FIG. 9 is a cross-section of an optical lens in accordance with a fourthembodiment of the disclosure.

FIG. 10 is a cross-section of an optical lens in accordance with a fifthembodiment of the disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to FIGS. 4 and 5, a light-emitting device 100 in accordancewith a first embodiment is shown. The light-emitting device 100 includesa light-emitting semiconductor unit 200, and an optical lens 300 coupledto the light-emitting semiconductor unit 200. The light-emitting device100 is a symmetrical body having a central axis 101 passing throughcenters of the light-emitting semiconductor unit 200 and the opticallens 300.

The light-emitting semiconductor unit 200 includes a package body 201,and a semiconductor chip 202 fixed on the package body 201. The packagebody 201 includes a protruding portion 2011 at a top end thereof, and aconnecting portion 2012 at an opposite bottom end thereof. Thesemiconductor chip 202 is disposed on a middle of the protruding portion2011. The connecting portion 2012 is configured for electricallyconnecting the semiconductor chip 202 to an external circuit (notshown). The semiconductor chip 202 has a light emitting PN (positivenegative) junction, and is configured for emitting light. Thesemiconductor chip 202 may be of any of various shapes, including acube, a rectangular block, a hemisphere, or other.

The optical lens 300 is symmetrical about the central axis 101. Forexample, the optical lens 300 can be cylindrically symmetrical about thecentral axis 101. The optical lens 300 includes a top surface 301, abase portion 304 opposite to the top surface 301, and a peripheral sidesurface (not labeled). The peripheral side surface has a corrugatedrefractive portion 302 and a smooth refractive portion 303 thereat. Thebase portion 304 has an inverted U-shaped cross-section taken along aplane passing through the central axis 101, and defines a cavity (notlabeled) receiving the protruding portion 2011 therein. Thus, thesemiconductor chip 202 disposed on the middle of the protruding portion2011 is protected. In alternative embodiments, the optical lens 300 maybe radially symmetrical about the central axis 101. That is, the opticallens 300 may be generally polyhedral, with the peripheral side surfacethereof being generally polygonal.

The optical lens 300 is made of transparent material, such as (but notlimited to) cyclic olefin copolymer (COC), polymethyl methacrylate(PMMA), polycarbonate (PC), PC/PMMA, silicone, fluorocarbon polymer, orpolyetherimide (PEI). The optical lens 300 may be manufacturedindependently using any of various well-known techniques, such asdiamond turning (i.e., the optical lens 300 is shaped by a lathe with adiamond bit), injection molding, or casting. Alternatively, the opticallens 300 may be integrally formed on the package body 201 having thesemiconductor chip 202 by any of various techniques such as (but notlimited to) injection molding (e.g., insert molding), or casting.

The top surface 301 is substantially funnel-shaped or cone-shaped. Ifthe optical lens 300 is cylindrically symmetrical about the central axis101, the top surface 301 has the same symmetrical double-curvedcross-section taken along any plane passing through the central axis101. The two curves of the symmetrical double-arc shape are convex, withthe top surface 301 being generally convex. That is, the top surface 301has a uniform curvature through 360° measured around the central axis101. Thereby, the top surface 301 provides a total internal reflectivesurface. This means the top surface 301 can effectively reflect light sothat the light exits the optical lens 300 through the corrugatedrefractive portion 302. If the optical lens 300 is radially symmetricalabout the central axis 101, the top surface 301 may have a symmetricaldouble-curved cross-section for a cross-section taken along a planepassing through the central axis 101, and may have two or more differentdouble-curved cross-sections taken along a plane passing through thecentral axis 101, depending on where the plane of the cross-sectionpasses through the central axis 101 is located, and depending on theparticular radially symmetrical configuration of the optical lens 300.That is, the top surface 301 includes a plurality of curved portionsconnected to each other. The curved portions cooperatively provide thetop surface 301 with a total internal reflective surface. Thereby, thetop surface 301 can effectively reflect light so that the light exitsthe optical lens 300 through the corrugated refractive portion 302.

The corrugated refractive portion 302 includes a top end (not labeled)connecting to the top surface 301, and a bottom end (not labeled)connecting to the smooth refractive portion 303. The bottom end of thecorrugated refractive portion 302 is configured to be lower than abottommost extremity of the top surface 301. The corrugated refractiveportion 302 includes a plurality of protruding ridge structures thatencircle or surround the optical lens 300 thereat. In the illustratedembodiment, the ridge structures are parallel to each other. Each of theridge structures has a triangular cross-section taken along a planepassing through the central axis 101. In the illustrated embodiment, thetriangular cross-sections of the ridge structures have the sameorientation. Each of the ridge structures includes an angled refractivesurface 3021. In the illustrated embodiment, the angled refractivesurfaces 3021 of the ridge structures are angled at the same anglerelative to the central axis 101. A desired light emitting angle of eachridge structure can be obtained by configuring the angle of therefractive surface 3021 accordingly. It should be understood that inalternative embodiments, the refractive surfaces 3021 may have differentangles. Thus, the light distribution characteristics of the corrugatedrefractive portion 302 can be configured as needed.

In one embodiment, the smooth refractive portion 303 has a cylindricalsurface. The smooth refractive portion 303 is configured for refractinglight that is directly received from the semiconductor chip 202, thatis, light that is not reflected by the top surface 301. The lightrefracted at the smooth refractive portion 303 then exits the opticallens 300.

Referring to FIG. 6, in use, a major portion of light emitted from thesemiconductor chip 202 transmits upwardly to the top surface 301. Thelight is then totally reflected by the top surface 301, and exits theoptical lens 300 through the corrugated refractive portion 302. A minorportion of the light emitted from the semiconductor chip 202 transmitsdirectly to the smooth refractive portion 303. The light is thenrefracted by the smooth refractive portion 303 and exits the opticallens 300.

Referring to FIG. 7, an optical lens 400 in accordance with a secondembodiment is similar to the optical lens 300 of the first embodiment.The optical lens 400 includes a top surface 401, a corrugated refractiveportion 402, and a smooth refractive portion 403. A bottom end of thecorrugated refractive portion 402 is configured to be higher than abottommost extremity of the top surface 401. The corrugated refractiveportion 402 includes a first refractive section 4022 and a secondrefractive section 4023. The first refractive section 4022 and thesecond refractive section 4023 each include a plurality of ridgestructures. Each of the ridge structures has a triangular cross-sectiontaken along a plane passing through a central axis of the optical lens400. The first refractive section 4022 includes a plurality of firstrefractive surfaces (not labeled) having the same first angle relativeto the central axis. The second refractive section 4023 includes aplurality of second refractive surfaces (not labeled) having the samesecond angle relative to the central axis. The first angle of the firstrefractive surfaces is different from the second angle of the secondrefractive surfaces. Desired light emitting angles of the firstrefractive section 4022 and the second refractive section 4023 can beobtained by configuring the respective angles accordingly. Thus, adesired light distribution characteristic of the corrugated refractiveportion 402 can be achieved.

Referring to FIG. 8, an optical lens 500 in accordance with a thirdembodiment is similar to the optical lens 300 of the first embodiment.The optical lens 500 includes a top surface 501, a first corrugatedrefractive portion 502, a second corrugated refractive portion 503, anda cylindrical side surface (not labeled). A bottom end of the secondcorrugated refractive portion 503 is configured to be lower than abottommost extremity of the top surface 501. The first corrugatedrefractive portion 502 includes a plurality of ridge structures, eachincluding a first refractive surface 5021. The second corrugatedrefractive portion 503 includes a plurality of ridge structures, eachincluding a second refractive surface 5032. The first refractivesurfaces 5021 have the same first angle relative to a central axis ofthe optical lens 500. The second refractive surfaces 5032 have the samesecond angle relative to the central axis of the optical lens 500. Inthe illustrated embodiment, the first angle is equal to the secondangle. However, the first refractive surfaces 5021 and the secondrefractive surfaces 5032 are oriented symmetrically relative to eachother. The first corrugated refractive portion 502 is configured forrefracting light that is received from a semiconductor chip (not shown)via the top surface 501, whereupon the refracted light exits the opticallens 500. The second corrugated refractive portion 503 is configured forrefracting light that is directly received from the semiconductor chip,whereupon the refracted light exits the optical lens 500.

Referring to FIG. 9, an optical lens 600 in accordance with a fourthembodiment is similar to the optical lens 300 of the first embodiment.The optical lens 600 includes a top surface 601, a corrugated refractiveportion 602, a smooth refractive portion 603, and a reflecting sheet604. The reflecting sheet 604 is disposed above the top surface 601. Thereflecting sheet 604 is configured for reflecting any light that escapesout of the top surface 601 back into the optical lens 600. Thereby, theefficiency of light utilization provided by the optical lens 600 can beimproved. In the illustrated embodiment, the reflecting sheet 604 is areflecting plate.

Referring to FIG. 10, an optical lens 700 in accordance with a fifthembodiment is similar to the optical lens 300 of the first embodiment.The optical lens 700 includes a top surface 701, a corrugated refractiveportion 702, a smooth refractive portion 703, and a reflecting film 704.The reflecting film 704 is located on the top surface 701. Thereflecting film 704 is configured for preventing any light from escapingfrom the top surface 701. Thereby, the efficiency of light utilizationprovided by the optical lens 700 can be improved, and the uniformity oflight output from the optical lens 700 enhanced.

It is believed that the present embodiments and their advantages will beunderstood from the foregoing description, and it will be apparent thatvarious changes may be made thereto without departing from the spiritand scope of the invention or sacrificing all of its materialadvantages, the examples hereinbefore described merely being preferredor exemplary embodiments of the invention.

1. A light emitting device, comprising: a light-emitting semiconductorunit; and an optical lens coupled to the light-emitting semiconductorunit, the optical lens comprising: a top surface; a base portionopposite to the top surface; and a peripheral side surface defining afirst refractive portion corrugated with a plurality of protruding ridgestructures, each including a first refractive surface.
 2. The lightemitting device as claimed in claim 1, wherein the light-emittingsemiconductor unit includes a package body disposed adjacent to a bottomof the optical lens and a semiconductor chip fixed on the package body.3. The light emitting device as claimed in claim 2, wherein the packagebody includes a protruding portion at an end thereof on which thesemiconductor chip is disposed, and the base portion defines a bottomcavity receiving the protruding portion bearing the semiconductor chipthereon.
 4. The light emitting device as claimed in claim 1, wherein theperipheral side surface further defines a second refractive portionincluding a top end adjacent to the top surface and a bottom endadjacent to the second refractive portion.
 5. The light emitting deviceas claimed in claim 4, wherein the second refractive portion iscorrugated with a plurality of protruding ridge structures, eachincluding a second refractive surface, symmetrically relative to each ofwhich each of the first refractive surfaces of the first refractiveportion is oriented.
 6. The light emitting device as claimed in claim 4,wherein the second refractive portion is cylindrical.
 7. The lightemitting device as claimed in claim 6, wherein the first refractiveportion includes a first refractive section and a second refractivesection, each including a plurality of ridge structures, each of whichhas a triangular cross-section, the ridge structures of the firstrefractive section including a plurality of first refractive surfaceshaving the same first angle relative to a central axis of the opticallens, the ridge structures of the second refractive section including aplurality of second refractive surfaces having the same second anglerelative to the central axis, and the first angle of the firstrefractive surfaces is different from the second angle of the secondrefractive surfaces.
 8. The light emitting device as claimed in claim 1,wherein the optical lens is made of a transparent material selected fromthe group consisting of cyclic olefin copolymer, polymethylmethacrylate, polycarbonate, silicone, fluorocarbon polymer, andpolyetherimide.
 9. The light emitting device as claimed in claim 1,wherein each of the ridge structures has a triangular cross-section,wherein the triangular cross-sections of the ridge structures have thesame orientation, and each of the ridge structures includes an angledrefractive surface, and the angled refractive surfaces of the ridgestructures are angled at the same angle relative to a central axis ofthe optical lens.
 10. The light emitting device as claimed in claim 1,wherein the optical lens further comprises a reflecting sheet above thetop surface.
 11. The light emitting device as claimed in claim 1,wherein the optical lens further comprises a reflecting film on the topsurface.